As an iron core, a non-oriented silicon steel having high magnetic permeability and low iron loss can be widely used not only in such rotation machines as compressor motors, motors for electric vehicles and small-sized precision motors, but also in such static machines as small-sized power transformers and voltage stabilizer. In recent years, with the increase of people's demands for portability and the decrease of non-renewable energy resources like coal, petroleum, etc., miniaturization and energy saving of electronic devices are required. In view of miniaturization of electronic devices, the non-oriented silicon steel is required to have a high magnetic permeability; and in view of energy saving of electronic devices, the non-oriented silicon steel is required to have a low iron loss. In addition, when used as an iron core in electronic devices such as rotation machines, the non-oriented silicon steel generally has a working magnetic flux density of 1.0˜1.5 T. Therefore, in order to realize the miniaturization and energy saving of electronic devices, it is expected to develop a non-oriented silicon steel having high magnetic permeability and low iron loss at a working magnetic flux density of 1.0˜1.5 T.
In order to improve the magnetic permeability and the iron loss of non-oriented silicon steel, many studies have been conducted, for example, increasing the purity of ingredients; using Al in combination with minor rare earth elements or Sb to improve a texture of the silicon steel; modifying impurities and oxide inclusions during a steel making; and making an improvement for cold rolling, hot rolling or final annealing process; and the like.
In U.S. Pat. No. 4,204,890, a non-oriented silicon steel having high magnetic permeability and low iron loss under a magnetic induction of 1.5 T is obtained by adding rare earth elements or trace element Sb, using a calcium treatment during steel making process and adopting a low-temperature treatment for long-time in a batch furnace.
In U.S. Pat. No. 4,545,827, a non-oriented silicon steel having excellent peak magnetic permeability and low iron loss is obtained by adjusting carbon content to control carbide precipitation and using temper rolling to obtain favorable ferrite grain size and easily magnetizable texture ingredients.
In U.S. Patent USRE35967, a non-oriented silicon steel having high peak magnetic permeability and low iron loss is obtained by subjecting an austenite zone to high-temperature hot rolling and final rolling at 1,720° and adopting a 0.5% temper rolling under small pressure after final annealing.
Although the above-mentioned prior techniques have made some progress in improving the magnetic permeability and the iron loss of non-oriented silicon steel, there are still some room for non-oriented silicon steel in improving its magnetic permeability and iron loss at a working magnetic flux density of 1.0˜1.5 T. It is expected to develop a non-oriented silicon steel having high magnetic permeability and low iron loss at a working magnetic flux density of 1.0˜1.5 T, which will meet the miniaturization and energy saving requirements of electronic devices such as rotation machines and static machines.